The purpose of the proposed research is to study the effects of both normal and abnormal physiological changes in the pulmonary circulation on one of the lung's important metabolic functions, the conversion of angiotensin I to angiotensin II. We shall make the measurements in a dog lung preparation in which pulmonary arterial and venous pressures may be easily controlled. We shall examine the effects on the conversion of angiotensin I to II of changing vascular pressures and therefore the volume of the capillaries and large vessels through which angiotensin I passes. The effects of changing mean transit time through the lungs and of alveolar hypoxia and other drugs such as histamine and serotonin on the conversion of angiotensin I to II will also be assessed. The bronchial circulation to the lungs will be perfused separately from the pulmonary circulation to see if conversion of angiotensin I occurs in these vessels. We shall also study the effects of 2 disease models in the dog's lungs on the conversion of angiotensin I to II. We shall produce a pathological disease resembling human emphysema by the intratracheal instillation of papain and a diffuse noncaseating granulomatous disease by the intravenous injection of Freund's adjuvant.